Molecular Characterization of UGT94F2 and UGT86C4, Two Glycosyltransferases from Picrorhiza kurrooa: Comparative Structural Insight and Evaluation of Substrate Recognition

Abstract

Uridine diphosphate glycosyltransferases (UGTs) are pivotal in the process of glycosylation for decorating natural products with sugars. It is one of the versatile mechanisms in determining chemical complexity and diversity for the production of suite of pharmacologically active plant natural products. Picrorhiza kurrooa is a highly reputed medicinal herb known for its hepato-protective properties which are attributed to a novel group of iridoid glycosides known as picrosides. Although the plant is well studied in terms of its pharmacological properties, very little is known about the biosynthesis of these important secondary metabolites. In this study, we identified two family-1 glucosyltransferases from P. kurrooa. The full length cDNAs of UGT94F4 and UGT86C4 contained open reading frames of 1455 and 1422 nucleotides, encoding polypeptides of 484 and 473 amino acids respectively. UGT94F2 and UGT86C4 showed differential expression pattern in leaves, rhizomes and inflorescence. To elucidate whether the differential expression pattern of the two Picrorhiza UGTs correlate with transcriptional regulation via their promoters and to identify elements that could be recognized by known iridoid-specific transcription factors, upstream regions of each gene were isolated and scanned for putative cis-regulatory elements. Interestingly, the presence of cis-regulatory elements within the promoter regions of each gene correlated positively with their expression profiles in response to different phytohormones. HPLC analysis of picrosides extracted from different tissues and elicitor-treated samples showed a significant increase in picroside levels, corroborating well with the expression profile of UGT94F2 possibly indicating its implication in picroside biosynthesis. Using homology modeling and molecular docking studies, we provide an insight into the donor and acceptor specificities of both UGTs identified in this study. UGT94F2 was predicted to be an iridoid-specific glucosyltransferase having maximum binding affinity towards 7-deoxyloganetin while as UGT86C4 was predicted to be a kaempferol-specific glucosyltransferase. These are the first UGTs being reported from P. kurrooa.

An endophyte of Picrorhiza kurroa Royle ex. Benth, producing menthol, phenylethyl alcohol and 3-hydroxypropionic acid, and other volatile organic compounds

“…Benth (Plantaginaceae) is a perennial herb endemic to the north western alpine Himalayas. Most of its pharmacological activities are attributed to the iridoid glycosides, known as picrosides (Stuppner and Wagner 1989;Bhat et al 2013). In this study, we report a novel endophyte, isolated from the rhizome of this plant, producing a combination of three important metabolites-menthol, phenyl ethyl alcohol and 3-hydroxypropionic acid.…”

Molecular characterization of two A-type P450s, WsCYP98A and WsCYP76A from Withania somnifera (L.) Dunal: expression analysis and withanolide accumulation in response to exogenous elicitations

“…The regulation pattern of squalene synthase, squalene epoxidase, cycloartenol synthase and WsCPR1 and WsCPR2 in leaves and roots at various developmental stages in relation to dynamics of withanolides accumulation, indicated towards their tissue-specific biosynthesis [ 22 ]. In our earlier findings, we have reported that exogenous application of methyl jasmonate (MeJA) and salicylic acid (SA) increases withanolide content due to the presence of stress regulatory elements within the upstream promoter regions of their genes [ 20 , 23 ].…”

Glycosylation of bioactive C13-apocarotenols inNicotiana benthamianaandMentha × piperita

“…Strikingly, picrocrocin was found in N. benthamiana when 3-hydroxy-β-cyclocitral was provided by CCD2, indicating apocarotenoid UGT activity in tobacco (Diretto et al 2019). Although UGT86C4 (Bhat et al 2013),…”